1. Field of the Invention
The present invention relates to an ink set for ink-jet recording to be used for a color ink-jet recording system, and to a ink-jet recording apparatus.
2. Description of the Related Art
The ink discharge system, which has been hitherto known as the ink-jet recording system, includes, for example, the electrostatic attraction system, the system in which mechanical vibration or displacement is applied to the ink by using a piezoelectric element or the like, and the method in which bubbles are generated by heating the ink to utilize the pressure generated thereby. Ink droplets are formed by means of the ink discharge system as described above, and all or a part of the ink droplets are adhered to a recording objective such as paper to perform the recording. Those known and used as the ink for ink-jet recording to be employed for the ink-jet recording system as described above include those in which a variety of water-soluble dyes or water-dispersible pigments are dissolved or dispersed in liquid media each comprising water or a combination of water and water-soluble organic solvent.
In order to adequately perform the recording for a long period of time by using the ink for ink-jet recording, for example, it is necessary to satisfy the following conditions. That is, the characteristic values including, for example, the viscosity, the surface tension, the electric conductivity, and the density of the ink for ink-jet recording to be used are appropriate values. The recorded image is excellent, for example, in water resistance and light resistance. In order to avoid any clog-up at the nozzle or the orifice of the recording apparatus, no deposited matter is generated and no physical property value is changed by the influence of heat or the like. A large number of suggestions have been made in order to satisfy the conditions as described above. For example, in order to avoid the clog-up at the nozzle or the orifice, a water-soluble organic solvent is generally added.
In order to obtain good printing qualities, exclusive ink-jet paper is sometimes used. However, in recent years, it is more demanded to perform the recording on the regular paper rather than the recording on the exclusive ink-jet paper, in view of the cost and the consideration of the environment. When the recording is performed on the regular paper with a plurality of conventional color inks, the following problem arises. That is, the color bleed is apt to occur, which is caused such that the inks of different colors are mixed with each other at portions at which the inks of different colors are adjacent to one another. As a result, the printing qualities are deteriorated. The blurring tends to be conspicuous at the ink boundary, for example, especially when letters or characters are recorded with a black ink having a relatively dark color on the background of a color ink having a relatively bright color such as yellow, magenta, or cyan.
In recent years, the black ink is progressively improved, for example, such that the pigment is used in order to vividly print letter portions. On the contrary, a problem has arisen as follows. That is, the blurring at the boundary is more conspicuous than before due to the high concentration of the letter portion and the vivid contrast.
In order to solve the problem as described above, a method is disclosed in Japanese Patent Application Laid-open No. 6-106841, in which a polyvalent metal salt is added into a color ink to aggregate an anionicity-added pigment in a black ink thereby so that the color bleed, which occurs when the black ink and the color ink are subjected to the recording adjacently, is reduced. However, if the polyvalent metal salt is added to the color ink in order to reduce the color bleed, a new problem arises such that the selection of the dye is restricted, because the dye, which is added into the color ink, is deposited in some cases. The deposition of the dye is conspicuous especially when the anionic dye is used. Further, as for a head for discharging the ink, a metal member is used for constructing the flow passage portion for the ink in many cases. A problem has arisen such that the metal member is apt to be corroded because the metal member always makes contact with the ink containing the polyvalent metal salt.
The present invention has been made in order to solve the problems as described above, an object of which is to provide an ink set for ink-jet recording which reduces the color bleed at the adjoining portions of a black ink and a color ink and which does not cause the deposition of the dye or the like in the color ink even when a plurality of colors are recorded on regular paper. Another object of the present invention is to provide an ink-jet recording apparatus which accommodates the ink set of the present invention.
According to a first aspect of the present invention, there is provided an ink for ink-jet recording comprising:
an anionic dye; and
at least one ethanolamine hydrochloride selected from the group consisting of monoethanolamine hydrochloride, diethanolamine hydrochloride, triethanolamine hydrochloride, and thioethanolamine hydrochloride. When the ink of the present invention is used together with an ink containing an anionicity-added pigment, the ethanolamine hydrochloride aggregates the anionicity-added pigment. Therefore, the color bleed is avoided at the adjoining portions of the inks. Further, pH is raised owing to the fact that the ethanolamine hydrochloride is contained. Therefore, the ink of the present invention prevents metal portions of the ink-jet recording apparatus from corrosion.
According to a second aspect of the present invention, there is provided an ink set for ink-jet recording comprising:
a first ink which contains an anionicity-added pigment; and
a second ink which contains an anionic dye and at least one ethanolamine hydrochloride selected from the group consisting of monoethanolamine hydrochloride, diethanolamine hydrochloride, triethanolamine hydrochloride, and thioethanolamine hydrochloride. When the ink-jet recording is performed by using the ink set of the present invention, the ethanolamine hydrochloride, which is contained in the second ink, aggregates the anionicity-added pigment which is contained in the first ink. Accordingly, the color bleed is avoided at the adjoining portions of the inks. Therefore, for example, when the ink-jet recording is performed by using the first ink as a black ink and using the second ink as a color ink, an extremely vivid color image is obtained.
According to a third aspect of the present invention, there is provided an ink-jet recording apparatus comprising:
an ink-jet head;
an ink tank which accommodates an ink to be supplied to the ink-jet head; and
an ink set according to the second aspect which is accommodated in the ink tank. The ink tank may includes a compartment in which the first and second inks are separately accommodated. The ink tank may be an ink container fixedly provided in the ink-jet recording apparatus or an ink cartridge which is replaceable. The second ink prevents metal portions of the ink-jet recording apparatus, for example, an ink flow passage from corrosion.